When a boat springs a leak, it's often the Coast Guard to the rescue. But who rescues the US Coast Guard when one its new ships does the same thing?

Captain Charles Cashin, who commands the Coast Guard's newest security cutter, the Stratton, said he called in engineers last month when his crew discovered a trio of "pinholes" and a fourth hole "slightly smaller than a golf ball" in the ship's hull.

Cashin said the four holes, discovered in mid-April while the ship was working off the coast of Los Angeles, have been patched for now but the Stratton soon will head to a dry dock for permanent repairs.

"The intent is to get out of the water," Cashin said. "We are literally just waiting for a contract."

The holes and other spots of rust on the hull are unusual, given the ship's age. The Coast Guard took delivery in September and Cashin and his crew put it in operation in October. The ship is based in Alameda, Calif.

The Stratton is third new 127-metre ship acquired as part of the Coast Guard's efforts to modernise its aging fleet.

Commander Chris O'Neil, a Coast Guard spokesman in Washington, said engineers aren't yet sure what why the ship is already having problems with rust and holes but they have concluded it is not a design problem in ship that cost the Coast Guard about US$500 million (NZ$620m). Similar problems have not been found in the fleet's two other ships of the same class.

Permanent repairs are likely to take four to six weeks, O'Neil said. He added that the Coast Guard is in contact with the ship's builder, Huntington Ingalls. The ship was constructed by Ingalls Shipbuilding of Pascagoula, Miss.

Beci Brenton, a company spokeswoman, declined to comment, pending further study and testing by the Coast Guard's engineers.

While he waits for repairs, Cashin said the Stratton is seaworthy.

"I am very confident in the safety of the ship and the crew," Cashin said.